Radio frequency ablation cooling shield

ABSTRACT

A medical assembly and method are provided to effectively treat abnormal tissue, such as, a tumor. The target tissue is thermally ablated using a suitable source, such as RF or laser energy. A cooling shield is placed in contact with non-target tissue adjacent the target tissue, and actively cooled to conduct thermal energy away from the non-target tissue. In one method, the cooling shield can be placed between two organs, in which case, one of the two organs can comprise the target tissue, and the other of the two organs can comprise the non-target tissue. In this case, the cooling shield may comprise an actively cooled inflatable balloon, which can be disposed between the two organs when deflated, and then inflated. The inflatable balloon can be actively cooled by pumping a cooling medium through it. In another method, the cooling shield can be embedded within the non-target tissue. In this case, the cooling shield can comprise one or more needles. If a plurality of needles is used, they can be embedded into the non-target tissue in a series, e.g., a rectilinear or curvilinear arrangement. The needle(s) can be actively cooled by pumping a cooling medium through them.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.11/462,961, filed Aug. 7, 2006 (now abandoned), which is a continuationof U.S. application Ser. No. 10/426,360, filed Apr. 30, 2003, now issuedas U.S. Pat. No. 7,101,387, the disclosure of which is herebyincorporated by reference.

The field of the invention generally relates to the structure and use ofablation to treat tissue abnormalities in a patient, and moreparticularly, to the use of radio frequency (RF) electrosurgical probesfor the treatment of such tissue.

BACKGROUND OF THE INVENTION

The delivery of radio frequency (RF) energy to target regions withintissue is known for a variety of purposes of particular interest to thepresent inventions. In one particular application, RF energy may bedelivered to diseased regions (e.g., tumors) in tissue for the purposeof tissue necrosis. RF ablation of tumors is currently performed withinone of two core technologies.

The first technology uses a single needle electrode, which when attachedto a RF generator, emits RF energy from the exposed, uninsulated portionof the electrode. This energy translates into ion agitation, which isconverted into heat and induces cellular death via coagulation necrosis.The second technology utilizes multiple needle electrodes, which havebeen designed for the treatment and necrosis of tumors in the liver andother solid tissues. PCT Publication WO 96/29946 and U.S. Pat. No.6,379,353 disclose such probes.

Whichever technique is used for treatment, the target site, e.g., thetumor, is often dangerously close to vital organs or tissue (e.g.,colon, prostate, gall bladder, or diaphragm). In many cases, to preventor reduce the risk of thermally injuring the vital organs or tissue, thephysician will opt to discontinue the procedure, or prematurely stop theprocedure, resulting in a high likelihood of re-occurrence.

Thus, there is a need for an improved system and method for protectingvital organs or tissue from thermal damage that may otherwise resultduring ablation of adjacent tissue.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present inventions, a medicalassembly for cooling tissue is provided. The medical assembly comprisesan elongate member and an inflatable cooling balloon mounted to theelongate member. The cooling balloon has an interior region and opposingplanar surfaces when inflated. The planar surfaces can be of any shape,e.g., rectangular or oval. The planar surfaces can be curved orstraight. The cooling balloon can be compliant, semi-compliant, ornon-compliant. In the preferred embodiment, the balloon is configured tobe placed between two distinct tissue layers, e.g., two organs.Depending upon the method of delivery, the elongate member can be rigidto facilitate, e.g., an open surgical or percutaneous introduction, orflexible to facilitate, e.g., a laparoscopic introduction. In oneembodiment, the elongate member comprises a guide wire lumen, so thatthe cooling balloon can be guided between the two layers of tissue.

The medical assembly further comprises cooling and return lumens thatextend through the elongate member in fluid communication with theinterior region of the cooling balloon. In the preferred embodiment, thecooling and return lumens are annular, but can have otherconfigurations. The medical assembly may comprise a cooling pumpassembly configured for pumping cooling medium (such as liquid or gas)through the cooling lumen into the interior region of the coolingballoon, and for pumping heated cooling medium from the interior regionof the cooling balloon through the return lumen.

Although the present inventions should not be so limited in its broadestaspects, the inflated balloon can be placed between ablation targetedtissue and non-target tissue in order to thermally protect thenon-target tissue during ablative treatment of the target tissue.

In accordance with a second aspect of the present inventions, anothermedical assembly for cooling tissue is provided. The medical assemblycomprises an elongated member and an army of actively cooled needlesextending from the distal end of the elongate member. The elongatemember can be rigid or flexible. The needle array is arranged in aseries. By way of non-limiting example, the array of needles can bearranged in a rectilinear or a curvilinear pattern, and can bestaggered, fan-shaped, or rake-shaped.

In the preferred embodiment, the needles are configured to be cooled bya liquid medium, such as liquid or gas. In this case, the medicalassembly may comprise a cooling pump assembly configured for pumpingcooling medium through the needles, and for pumping heated coolingmedium from the needles. In one embodiment, the medical assemblycomprises a cannula, wherein the elongate member is slidably disposedwithin the cannula, such that the array of needles can be selectivelydeployed from the cannula and retracted within the cannula. The cannulacan be configured to be introduced percutaneously or laparoscopicallyinto the body of a patient.

Although the present inventions should not be so limited in its broadestaspects, the needle array can be embedded within the tissue along aborder between tissue targeted to be ablated and non-target tissue inorder to thermally protect the non-target tissue during ablativetreatment of the target tissue.

In accordance with a third aspect of the present inventions, a method ofperforming an ablation procedure is provided. The method comprisesthermally ablating target tissue, e.g., a tumor, of a patient. Theablation can be performed using any suitable source of energy, such as,e.g., RF or laser energy. The method further comprises placing a coolingshield in contact with non-target tissue a adjacent the target tissue,and actively cooling the cooling shield to conduct thermal energy awayfrom the non-target tissue. If the non-target tissue is within the bodyof the patient, the cooling shield can be variously introduced thereinusing a suitable technique, such as, e.g., percutaneously,laparoscopically, or via a surgical opening

By way of non-limiting example, the cooling shield can be placed betweentwo organs, in which case, one of the two organs can comprise the targettissue, and the other of the two organs can comprise the non-targettissue. In this case, the cooling shield may comprise an actively cooledinflatable balloon, which can be disposed between the two organs whendeflated, and then inflated. The inflatable balloon can be guidedbetween the two organs using a guide wire. The inflatable balloon can beactively cooled by pumping a cooling medium through it.

By way of further non-limiting example, the cooling shield can beembedded within the non-target tissue. In this case, the cooling shieldcan comprise one or more needles. If a plurality of needles is used,they can be embedded into the non-target tissue in a series, e.g., arectilinear or curvilinear arrangement. The needle(s) can be activelycooled by pumping a cooling medium through them.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail though the use of the accompanying drawings inwhich:

FIG. 1 is a plan view of a tissue treatment system constructed inaccordance with one preferred embodiment of the present inventions;

FIG. 2 is a side view of an ablation probe assembly used in the tissuetreatment system of FIG. 1, wherein a needle electrode array isparticularly shown retracted;

FIG. 3 is a side view of an ablation probe assembly used in the tissuetreatment system of FIG. 1, wherein the needle electrode array isparticularly shown deployed;

FIG. 4 is a perspective view of a cooling probe used in the tissuetreatment system of FIG. 1;

FIG. 5 is a partially out-away cross-sectional view of the cooling probeof FIG. 4;

FIG. 6 is a cross-sectional view of the cooling probe of FIG. 5 takenalong the line 6-6;

FIG. 7A-7G-illustrate cross-sectional views of one preferred method ofusing the tissue treatment system of FIG. 1 to treat target tissue,wherein the cooling probe of FIG. 4 is used to thermally protectadjacent tissue;

FIG. 8 is a side view of a cooling probe that can be used in the tissuetreatment system of FIG. 1, particularly showing a needle array in arectilinear configuration;

FIG. 9 is a side view of a cooling probe that can be used in the tissuetreatment system of FIG. 1, particularly showing a needle array in acurvilinear configuration;

FIG. 10 is a side view of a cooling probe that can be used in the tissuetreatment system of FIG. 1, particularly showing a needle array in astaggered configuration;

FIG. 11 is a side view of a cooling probe that can be used in the tissuetreatment system of FIG. 1, particularly showing a needle array in arake-shaped configuration;

FIG. 12A-12B illustrate cross-sectional views of another preferredmethod of using the tissue treatment system of FIG. 1 to treat targettissue, wherein the cooling probe of FIG. 8 is used to thermally protectadjacent tissue;

FIG. 13 is a side view of another cooling probe that can be used in thetissue treatment system of FIG. 1, particularly showing the needle arrayretracted;

FIG. 14 is a side view of the cooling probe of FIG. 13 that can be usedin the tissue treatment system of FIG. 1, particularly showing theneedle array deployed into a fan-shaped configuration;

FIG. 15 is a partially cutaway view of an inner probe used in thecooling probe of FIG. 13;

FIG. 16A-16B illustrate cross-sectional views of still another preferredmethod of using the tissue treatment system of FIG. 1 to treat targettissue, wherein the cooling probe of FIG. 13 is used to thermallyprotect adjacent tissue;

FIG. 17 is a side view of another cooling probe that can be used in thetissue treatment system of FIG. 1; and

FIGS. 18A-18B illustrate cross-sectional views of yet another preferredmethod of using the tissue treatment system of FIG. 1 to treat targettissue, wherein the cooling probe of FIG. 17 is used to thermallyprotect adjacent tissue.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a tissue treatment system 100 constructed inaccordance with a preferred embodiment of the present inventions. Thetissue treatment system 100 comprises a tissue ablation subsystem 102,which generally includes an ablation probe assembly 106 configured forintroduction into the body of a patient for ablative treatment of targettissue (e.g., a tumor), and a radio frequency (RF) generator 108configured for supplying RF energy to the ablation probe assembly 106 ina controlled manner. The tissue treatment system 100 further comprises atissue cooling subsystem 104, which generally includes a cooling probe110 with an associated active cooling shield 112 configured for beingeffectively placed in contact with non-target tissue (e.g., a vitalorgan adjacent the tumor), and an active cooling unit 114 configured foractively removing thermal energy away from the cooling shield 112, andthus, the non-target tissue, during the ablation procedure.

Referring specifically to FIGS. 2 and 3, the ablation probe assembly 106generally comprises an elongate cannula 116 and an inner probe 118slidably disposed within the cannula 116. As will be described infurther detail below, the cannula 116 serve to deliver the activeportion of the inner probe 118 to the target tissue. The cannula 116 hasa proximal end 120, a distal end 122, and a central lumen 124 (shown inphantom) extending between the proximal and distal ends 120 and 122. Aswill be described in further detail below, the cannula 116 may be rigid,semirigid, or flexible depending upon the designed means for introducingthe cannula 116 to the target tissue. The cannula 116 is composed of asuitable material, such as plastic, metal, or the like, and has asuitable length, typically in the range from 5 cm to 30 cm, preferablyfrom 10 cm to 20 cm. If composed of an electrically conductive material,the cannula 108 is preferably covered with an insulative material. Thecannula 116 has an outside diameter consistent with its intended use,typically being from 1 mm to 5 mm, usually from 1.3 mm to 4 mm. Thecannula 116 has an inner diameter in the range from 0.7 mm to 4 mm,preferably from 1 mm to 3.5 mm.

The inner probe 118 comprises a reciprocating shaft 126 having aproximal end 128 and a distal end 130, and an array 132 of tissuepenetrating needle electrodes 134 extending from the distal end 130 ofthe shaft 126. Like the cannula 116, the shaft 126 is composed of asuitable material, such as plastic, metal or the like. It can beappreciated that longitudinal translation of the shaft 126 relative tothe cannula 116 in a distal direction 136 deploys the electrode array132 from the distal end 122 of the cannula 116 (FIG. 3), andlongitudinal translation of the shaft 126 relative to the cannula 116 ina proximal direction 138 retracts the electrode array 132 into thedistal end 122 of the cannula 116 (FIG. 2).

Each of the individual needle electrodes 134 is in the form of a smalldiameter metal element, which can penetrate into tissue as it isadvanced from a target site within the target region. When retractedwithin the cannula 116 (FIG. 2), the electrode array 132 is placed in aradially collapsed configuration, and the individual needle electrodes134 are constrained and held in generally axially aligned positionswithin the cannula 116 to facilitate its introduction to the tissuetarget site. The ablation probe assembly 106 optionally includes a coremember (not shown) mounted to the distal tip of the shaft 126 anddisposed within the center of the electrode array 132. In this manner,substantially equal circumferential spacing between the needleelectrodes 134 is maintained when retracted within the central lumen 124of the cannula 116.

When deployed from the cannula 116 (FIG. 3), the electrode array 132 isplaced in a three-dimensional configuration that usually defines agenerally ellipsoidal or spherical volume having a periphery with amaximum radius in the range from 0.5 cm to 3 cm. The needle electrodes134 are resilient and pre-shaped to assume a desired configuration whenadvanced into tissue. In the illustrated embodiment, the needleelectrodes 134 diverge radially outwardly from the cannula 116 in auniform pattern, i.e., with the spacing between adjacent needleelectrodes 134 diverging in a substantially uniform and/or symmetricpattern. In the illustrated embodiment, the needle electrodes 134 alsoevert proximally, so that they face partially or fully in the proximaldirection 138 when fully deployed. In exemplary embodiments, pairs ofadjacent needle electrodes 134 can be spaced from each other in similaror identical, repeated patterns that can be symmetrically positionedabout an axis of the shaft 126. It will be appreciated that a widevariety of particular patterns can be provided to uniformly cover theregion to be treated. It should be noted that a total of six needleelectrodes 134 are illustrated in FIG. 3. Additional needle electrodes134 can be added in the spaces between the illustrated electrodes 134,with the maximum number of needle electrodes 134 determined by theelectrode width and total circumferential distance available (i.e., theneedle electrodes 134 could be tightly packed).

Each individual electrode 134 is preferably composed of a single wirethat is formed from resilient conductive metals having a suitable shapememory, such as stainless steel, nickel-titanium alloys, nickel-chromiumalloys, spring steel alloys, and the like. The wires may have circularor non-circular cross-sections, but preferably have rectilinearcross-section. In this manner, the needle electrodes 134 are generallystiffer in the transverse direction and more flexible in the radialdirection. By increasing transverse stiffness, proper circumferentialalignment of the needle electrodes 134 within the cannula 116 isenhanced. Exemplary needle electrodes will have a width (in thecircumferential direction) in the range from 0.2 mm to 0.6 mm,preferably from 0.35 mm to 0.40 mm, and a thickness (in the radialdirection) in the range from 0.05 mm to 0.3 mm, preferably from 0.1 mmto 0.2 mm.

The distal ends of the needle electrodes 134 may be honed or sharpenedto facilitate their ability to penetrate tissue. The distal ends ofthese needle electrodes 134 may be hardened using conventional heattreatment or other metallurgical processes. They may be partiallycovered with insulation, although they will be at least partially freefrom insulation over their distal portions. The proximal ends of theneedle electrodes 134 may be directly coupled to the connector assembly(described below), or alternatively, may be indirectly coupled theretovia other intermediate conductors, e.g., RF wires. Optionally, the shaft126 and any component between the shaft 126 and the needle electrodes134, are composed of an electrically conductive material, such astainless steel, and may therefore conveniently serve a intermediateelectrical conductors.

In the illustrated embodiment, the RF current is delivered to theelectrode array 132 in a monopolar fashion, which means that currentwill pass from the electrode array 132, which is configured toconcentrate the energy flux in order to have an injurious effect on thesurrounding tissue, and a dispersive electrode (not shown), which islocated remotely from the electrode array 132 and has a sufficientlylarge area (typically 130 cm2 for an adult), so that the current densityis low and non-injurious to surrounding tissue. As previously described,however, inadvertent damage to surrounding tissue cannot always beavoided. In the illustrated embodiment, the dispersive electrode may beattached externally to the patient, e.g., using a contact pad placed onthe patient's flank. In a monopolar arrangement, the needle electrodes134 are bundled together with their proximal portions having only asingle layer of insulation over the cannula 116.

Alternatively, the RF current is delivered to the electrode array 132 ina bipolar fashion, which means that current will pass between “positive”and “negative” electrodes 134 within the array. In a bipolararrangement, the positive and negative needle electrodes 134 will beinsulated from each other in any regions where they would or could be incontact with each other during the power delivery phase.

Further details regarding needle electrode array-type probe arrangementsare disclosed in U.S. Pat. No. 6,379,353, entitled “Apparatus and Methodthe Treating Tissue with Multiple Electrodes,” which is hereby expresslyincorporated herein by reference.

The ablation probe assembly 106 further comprises a handle assembly 140,which includes a connector sleeve 142 mounted to the proximal end 120 ofthe cannula 116 and a connector member 144 slidably engaged with thesleeve 142 and mounted to the proximal end 128 of the shaft 126. Theconnector member 144 also comprises an electrical connector 146 (inphantom) in which the proximal ends of the needle electrodes 134 (oralternatively, the intermediate conductors) extending through the shaft126 of the inner probe 118 are coupled. The handle assembly 140 can becomposed of any suitable rigid material, such as, e.g., metal, plastic,or the like.

The ablation probe assembly 106 may optionally have active coolingfunctionality, in which case, a heat sink (not shown) can be mountedwithin the distal end 130 of the shaft 126 in thermal communication withthe electrode array 132, and cooling and return lumens (not shown) canextend through the shaft in fluid communication with the heat sink todraw thermal energy away back to the proximal end of the shaft 126. Apump assembly (not shown) can be provided to convey a cooling mediumthrough the cooling lumen to the heat sink, and to pump the heatedcooling medium away from the heat sink and back through the returnlumen. Further details regarding active cooling of the electrode array132 are disclosed in copending U.S. application Ser. No. 10/426,360.

Referring back to FIG. 1, the RF generator 108 is electrically connectedto the electrical connector 146 of the handle assembly 140, which aspreviously described, is directly or indirectly-electrically coupled tothe electrode array 132. The RF generator 108 is a conventional RF powersupply that operates at a frequency in the range of 200 KHz to 1.25 MHz,with a conventional sinusoidal or non-sinusoidal wave form. Such powersupplies are available from many commercial suppliers, such asValleylab, Aspen, and Bovie. Most general purpose electrosurgical powersupplies, however, operate at higher voltages and powers than wouldnormally be necessary or suitable for vessel occlusion.

Thus, such power supplies would usually be operated at the lower ends oftheir voltage and power capabilities. More suitable power supplies willbe capable of supplying an ablation current at a relatively low voltage,typically below 150V (peak-to-peak), usually being from 50V to 100V. Thepower will usually be from 20 W to 200 W, usually having a sine waveform, although other wave forms would also be acceptable. Power suppliescapable of operating within these ranges are available from commercialvendors, such as RadioTherapeutics of Mountain View, Calif., whichmarkets these power supplies under the trademarks RF2000™ (100 W) andRF3000™ (200 W).

Referring now to FIG. 4, the cooling probe 110 comprises an elongatecatheter shaft 150 having a proximal end 152 and a distal end 154. Thecatheter shaft 150 is composed of a flexible biocompatible material,such as, e.g., polyurethane or polyethylene, and has a suitablediameter, e.g., 7F. In this embodiment; the cooling shield 112 is aninflatable balloon that is mounted to the distal end 154 of the cathetershaft 150. In the illustrated embodiment, the balloon 112 is bonded tothe catheter shaft 150 by a suitable adhesive, for example, epoxyadhesives, urethane adhesives, cyanoacrylates, and other adhesivessuitable for bonding nylon or the like, as well as by hot melt bonding,ultrasonic welding, heat fusion or the like. Alternatively, the balloonmay be integrally molded with the catheter shaft 150 or may be attachedto the catheter shaft 150 by mechanical means such as swage locks, crimpfittings, threads, and the like.

As illustrated in FIG. 4, the balloon 112 exhibits a substantially thinprofile, when expanded, so that it can be effectively located betweenadjacent planes of tissue such as, e.g., two organs. That is, theballoon 112 has a pair of opposing planar surfaces 156 and 158 that arelaterally spaced from each other a small distance, so that the expandedballoon 112 can easily fit between and conform to the adjacent planes oftissue. The planar surfaces 156 and 158 of the balloon 112 have arectangular shape, but can have other shapes (e.g., oval, oblong,triangular, trapezoidal, etc.) depending upon the specific tissue planesbetween which the balloon 112 is intended to be located. It is notedthat, in the illustrated embodiment, the planar surfaces 156 and 158 arecurved, so that the balloon 112 will conform to the curved surface of anorgan. The balloon 112 can be of any dimension that allows it to beeffectively placed between the desired planes of tissue, so that thenon-target tissue is protected.

The balloon 112 can be composed of a suitable compliant, semi-compliant,or non-compliant, such as, e.g., polyethylene, nylon, polyamide,polyether block amides (PEBAX), polyethylene terephthalate (PET),silicone, POC, polypropylene, polyether block PBT, and the like. Inaddition, the balloon 112 may be formed of multiple layers of thesematerials and/or be coextruded. Further, the balloon 112 may comprisefiber reinforcements.

Preferably, the balloon 112 exhibits some non-compliancy so that it caninflate between the adjacent planes of tissue. If non-compliant, theballoon 112 can be manually folded or collapsed onto the distal end 154of the catheter shaft 150 and held in place using suitable securingmeans (not shown) to maintain a low profile when introduced into thebody of the patient. The securing means can then be released when theballoon 112 is to be inflated. If the balloon 112 exhibits enoughcompliancy, the balloon 112 will naturally have a low profile whendeflated, possibly obviating the need to manually fold or collapse theballoon 112. Depending upon its size, however, the balloon 112, whethercompliant or not, may need to be folded and secured to ensure that itexhibits a low profile when not inflated.

Referring now to FIGS. 5 and 6, the catheter shaft 150 comprises anouter tubular element 160, an inner tubular element 162 that resideswithin, and extends distally from, the outer tubular element 160, and acentral tubular element 164 that resides within, and extends distallyfrom, the inner tubular element 162. The cooling probe 110 comprises acoolant flow conduit that is in fluid communication with an interiorregion 166 of the balloon 112. The coolant flow conduit serves to coolthe external surface of the balloon 112, and thus the tissue in contactwith the balloon 112, by thermally drawing heat away from the balloon112. In particular, the coolant flow conduit comprises a cooling lumen168 that is configured for conveying a suitable cooling medium (such as,e.g., a liquid or gas) into the interior region 166 of the balloon 112,and a return lumen 170 that is configured for conveying the heatedcooling medium from the interior region 166 of the balloon 112.Preferably, the cooling medium is composed of saline that is cooled tojust above the cryotemperature that would cause unintended necrosis oftissue. It should be noted that for the purposes of this specification,however, a cooled medium is any medium that has a temperature suitablefor drawing heat away from the tissue. For example, a cooled medium atroom temperature or lower may be suited for cooling tissue duringablation under certain circumstances.

In the illustrated embodiment, the cooling lumen 168 is an annular lumenthat is formed between the inner and central tubular elements 162 and164, and the return lumen 170 is an annular lumen that is formed betweenthe outer and inner tubular elements 160 and 162. Alternatively, theannular lumen formed between the inner and central tubular elements 162and 164 can be the return lumen 170, and the annular lumen formedbetween the outer and inner tubular elements 160 and 162 can be thecooling lumen 168. It should be noted that the cooling and return lumens168 and 170 need not be coaxial, but can be disposed within the cathetershaft 150 in a side-by-side relationship. In any event, the cooling andreturn lumens 168 and 170 preferably terminate in opposite ends of theinterior region 166 of the balloon 112 to provide a more efficient flowof the medium through the interior region 166 of the balloon 112 (asshown by the arrows), i.e., the medium will flow through the entirelength of the balloon 112.

Referring back to FIG. 4, the cooling probe 110 further comprises ahandle 172 mounted to the proximal end 152 of the catheter shaft 150.The handle 172 is configured to mate with the active cooling unit 114,which as will be discussed below, takes the form of a pump assembly. Tothis end, the handle 172 comprises an inlet fluid port 174, which is influid communication with the cooling lumen 168, and an outlet fluid port176, which is in fluid communication with the return lumen 170. Thehandle assembly 140 can be composed of any suitable rigid material, suchas, e.g., metal, plastic, or the like.

In the illustrated embodiment, the cooling probe 110 is configured to belaparoscopically introduced into the pertinent body cavity of thepatient and guided between the tissue planes with a guide wire. To thisend, the cooling probe 110 comprises a guide wire lumen 178 (shown inFIG. 5), which is formed by the central lumen of the central tubularelement 164. So that the cooling probe 110 can be tracked over the guidewire, the catheter shaft 150 is preferably composed of a flexiblebiocompatible material. Alternatively, a semi-rigid sheath can be usedto guide the cooling probe 110. Even more alternatively, the coolingprobe 110 may be configured to be percutaneously inserted into thepertinent body cavity (e.g., using a direct chest puncture), in whichcase, a rigid shaft can be used in place of the flexible catheter shaft150. The rigid shaft can also be reciprocatably disposed within acannula 116 in a manner similar to that described above with respect tothe ablation probe assembly 106. The rigid shaft can even be used tofacilitate manual placement of the balloon 112 in an open surgicalsetting with or without the cannula.

Referring back to FIG. 1, the pump assembly 114 comprises a power head180 and a syringe 182 that is front-loaded on the power head 180 and isof a suitable size, e.g., 200 ml. The power head 180 and the syringe 182are conventional and can be of the type described in U.S. Pat. No.5,279,569 and supplied by Liebel-Flarsheim Company of Cincinnati, Ohio.The pump assembly 114 further comprises a source reservoir 184 forsupplying the cooling medium to the syringe 182, and a dischargereservoir 186 for collecting the heated medium from cooling probe 110.The pump assembly 114 further comprises a tube set 188 removably securedto an outlet 190 of the syringe 182. Specifically, a dual check valve192 is provided with first and second legs 194 and 196, of which thefirst leg 194 serves as a liquid inlet connected by tubing 197 to thesource reservoir 184. The second leg 196 is an outlet leg and isconnected by tubing 198 to the inlet fluid port 174 on the connector 170of the cooling probe 110. The discharge reservoir 186 is connected tothe outlet fluid port 176 on the connector 170 of the cooling probe 110via tubing 199.

Thus, it can be appreciated that the pump assembly 114 can be operatedto periodically fill the syringe 182 with the cooling medium from thesource reservoir 184, and convey the cooling medium from the syringe182, through the tubing 198, and into the inlet fluid port 174 on thehandle 172. Heated medium is conveyed from the outlet fluid port 176 onthe handle 172, through the tubing 198, and into the collectionreservoir 186. The pump assembly 114, along with the RF generator 108,can include control circuitry to automate or semi-automate the cooledablation process.

Having described the structure of the tissue ablation system 100, itsoperation in treating targeted tissue will now be described. Thetreatment region may be located anywhere in the body where hyperthermicexposure may be beneficial. Most commonly, the treatment region willcomprise a solid tumor within an organ of the body, such as the liver,kidney, pancreas, breast, prostrate (not accessed via the urethra), andthe like. The volume to be treated will depend on the size of the tumoror other lesion, typically having a total volume from 1 cm3 to 150 cm3,and often from 2 cm3 to 35 cm3. The peripheral dimensions of thetreatment region may be regular, e.g., spherical or ellipsoidal, butwill more usually be irregular. The treatment region may be identifiedwing conventional imaging techniques-capable of elucidating a targettissue, e.g., tumor tissue, such as ultrasonic scanning, magneticresonance imaging (MRI), computer-assisted tomography (CAT),fluoroscopy, nuclear scanning (using radiolabeled tumor-specificprobes), and the like. Preferred is the use of high resolutionultrasound of the tumor or other lesion being treated, eitherintraoperatively or externally. A contrast agent, such as an echogenicfluid, can be used as the cooled medium, so that the balloon 112 of thecooling probe 110 can be visualized using.

Referring now to FIGS. 7A-7G, the operation of the tissue treatmentsystem 100 is described in treating a treatment region TR within atissue T located beneath the skin or an organ surface S of a patient.The tissue T, and an adjacent organ 0, prior to treatment is shown inFIG. 7A. The ablation probe assembly 106 is introduced within thetreatment region TR, so that the distal end 122 of the cannula 116 islocated at the target site TS, as illustrated in FIG. 7B. This can beaccomplished using any one of a variety of techniques. In some cases,the cannula 116 and inner probe 118 may be introduced to the target siteTS percutaneously directly through the patient's skin or through an opensurgical incision. In this case, the cannula 116 may have a sharpenedtip, e.g., in the form of a needle, to facilitate introduction to thetreatment region TR. In such cases, it is desirable that the cannula 116or needle be sufficiently rigid, i.e., have a sufficient columnstrength, so that it can be accurately advanced through tissue. In othercases, the cannula 116 may be introduced using an internal stylet thatis subsequently exchanged for the shaft 150 and electrode array 132. Inthis latter case, the cannula 116 can be relatively flexible, since theinitial column strength will be provided by the stylet. Morealternatively, a component or element may be provided for introducingthe cannula 116 to the treatment region TR. For example, a conventionalsheath and sharpened obturator (stylet) assembly can be used toinitially access the tissue T. The assembly can be positioned underultrasonic or other conventional imaging, with the obturator/stylet thenremoved to leave an access lumen through the sheath. The cannula 116 andinner probe 118 can then be introduced through the sheath lumen, so thatthe distal end 122 of the cannula 116 advances from the sheath into thetarget site TS.

A guide wire 175 is then laparoscopically introduced within the body ofthe patient and advanced to a location between the treatment region TRand the organ 0, as illustrated in FIG. 7C. The cooling probe 110 isthen advanced over the guide wire 175 until the uninflated balloon 112resides between the treatment region TR and the organ 0, as illustratedin FIG. 7D. Alternatively, the cooling probe 110 can percutaneously orlaparoscopically deliver the balloon 112 between the treatment region TRwithout the use of the guide wire 175 in the same manner that theablation probe assembly 106 is delivered to the treatment region TR.

After the cannula 116 and cooling probe 110 are properly placed, theshaft 150 of the ablation probe assembly 106 is distally advanced todeploy the electrode array 132 radially outward from the distal end 122of the cannula 116 until the electrode array 132 fully everts in orderto circumscribe substantially the entire treatment region TR, asillustrated in FIG. 7E.

The RF generator 108 is then connected to the electrical connector 146of the ablation probe assembly 106, and the pump assembly 114 isconnected to fluid ports 174 and 176 of the cooling probe 110. The pumpassembly 114 is then operated to inflate and convey the cooling mediumthrough the balloon 112, thereby providing a thermal barrier between thetreatment region TR and the organ 0, as illustrated in FIG. 7F.Specifically, the power bead 180 conveys the cooled medium from thesyringe 182 under positive pressure, through the tubing 198, and intothe inlet fluid port 174 on the handle 172. The cooled medium thentravels through the cooling lumen 168 and into the interior region 166of the balloon 112. Thermal energy is transferred from the treatmentregion TR, to the balloon 112, and then to the cooled medium, therebypreventing the thermal energy from reaching the organ 0 at a cooltemperature. The heated medium is then conveyed from the interior regionof the balloon 112 back through the return lumen 170. From the returnlumen 170, the heated medium travels through the outlet fluid port 176on the handle 172, through the tubing 199, and into the dischargereservoir 186.

The RF generator 108 is then operated to ablate the treatment region TR.Specifically, a lesion L is formed within the treatment region TR, asillustrated in FIG. 7G. Because the actively cooled balloon 112 forms athermal barrier between the treatment region TR and the organ 0, thelesion L does not extend to the organ 0.

Referring to FIG. 8, another cooling probe 210 that can be used in thecooling subsystem 104 is illustrated. The cooling probe 210 comprises ashaft 212 having a proximal end 214 and a distal end 216. The coolingprobe 210 further comprises a handle 218 mounted to the proximal end 214of the shaft 212, and across-member 220 mounted to the distal end 216 ofthe shaft 212. The cross-member 220 can be integrally formed with theshaft 212 to form a unibody design, or can be suitably bonded, welded,or mechanically attached to the shaft 212. Like the previously describedhandle assembly 140, the handle 218 comprises an inlet fluid port 222and an outlet fluid port 224. In this embodiment, the cooling shield 112comprises an array 226 of tissue penetrating cooling needles 228 that ismounted to the cross-member 220. The needles 228 can be integrallyformed with the cross-member to form a unibody design, or can besuitably bonded, welded, or mechanically attached to the cross-member220. The shaft 212, cross-member 220, and needles 228 are formed of asuitable rigid material, such as, e.g., stainless steel. The diameterand length of the needles 228 are preferably within the range of 0.5 mmto 4.0 mm, and 5 cm to 25 cm, respectively.

As illustrated in FIG. 8, the needles 228 are arranged in a series tomaximize the cooling efficiency of cooling probe 210, i.e., the span ofthe needle array 226 is maximized, thereby allowing larger non-targettissue regions to be thermally protected. In the illustrated embodiment,the needle array 226 is arranged in a rectilinear pattern. It should benoted, that depending upon the contour of the non-target tissue, theneedle array 226 can also be arranged in a curvilinear pattern, asillustrated in FIG. 9. The needles 228 can also be staggered ifadditional thermal protection is required, as illustrated in FIG. 10.Although, in the illustrated embodiment, the needles 228 are shownparallel to each other, they can also be non-parallel, e.g., arake-shape, as illustrated in FIG. 11.

Referring back to FIG. 8, the cooling probe 210 further comprises acoolant flow conduit (shown in phantom) that serves to cool the needles228, and thus the tissue in contact with the balloon 112, by thermallydrawing heat away. In particular, the coolant flow conduit comprises amain cooling lumen 230 that is in fluid communication with the inletfluid port 222 of the handle 218 and extends through the shaft 212, acommon cooling lumen 234 that is in fluid communication with the maincooling lumen 230 and extends through the cross-member 220, and aplurality of branched cooling lumens 238 that is in fluid communicationwith the common cooling lumen 234 and extends through the needles 228.The coolant flow conduit also comprises a main return lumen 232 that isin fluid communication with the outlet fluid port 224 of the handle 218and extends through the shaft 212, a common return lumen 236 that is influid communication with the main return lumen 232 and extends throughthe cross-member 220, and a plurality of branched return lumens 240 thatis in fluid communication with the common return lumen 236 and extendsthrough the needles 228. The distal ends of the branched cooling lumens238 are in fluid communication with the respective distal ends of thebranched return lumens 240 to complete the cooling circuit.

Operation of the cooling probe 210 is similar to that previouslydescribed with the exception that it is designed to be inserted into thetissue during an open surgical setting. Specifically, the electrodearray 132 of the ablation probe assembly 106 is deployed within thetarget tissue TR, as illustrated in FIG. 7. The needle array 226 of thecooling probe 210 is inserted within the tissue, so that the needles 228lie along a boundary B separating the treatment region TR from thenon-treatment region NTR, as illustrated in FIG. 12A.

The pump assembly 114 is then operated to convey the cooling mediumthrough the needles 228, thereby providing a thermal barrier between thetreatment region TR and the non-treatment region NTR. Specifically, thepower head 180 conveys the cooled medium from the syringe 182 underpositive pressure, through the tubing 198, and into the inlet fluid port222 on the handle 218. The cooled medium then travels through the maincooling lumen 230, through the common cooling lumen 234, and into thebranched cooling lumens 238 within the needles 228. Thermal energy istransferred from the treatment region TR, to the needles 228, and thento the cooled medium, thereby preventing the thermal energy fromreaching the non-treatment region NTR and maintaining it at a codtemperature. The heated medium is then conveyed from the branched returnlumens 240, through the common return lumen 236, and through the mainreturn lumen 232. From the main return lumen 232, the heated mediumtravels through the outlet fluid pot 224 on the handle 218, through thetubing 199, and into the discharge reservoir 186.

The RF generator 108 is then operated to ablate the treatment region TR.Specifically, a lesion L is formed within the treatment region TR, asillustrated in FIG. 12B. Because the actively cooled needle array 226forms a thermal barrier between the treatment region TR and thenon-treatment region NTR, the lesion L does not extend to thenon-treatment NTR, but instead exhibits a scalloped contour that extendsalong the barrier B.

Referring to FIGS. 13 and 14, a cooling probe 310 that can be used inthe cooling subsystem 104 is illustrated. The cooling probe 310 isgenerally similar in structure to the ablation probe assembly 106 inthat it comprises an elongate cannula 312 and an inner probe 314slidably disposed within the cannula 312. The cannula 312 has a proximalend 316, a distal end 318, and a central lumen 320 (shown in phantom)extending between the proximal and distal ends 316 and 318. The cannula312 can have a dimension and composition similar to that described abovewith respect to the cannula 116 of the ablation probe assembly 106. Theinner probe 314 comprises a reciprocating shaft 322 (shown best in FIG.15) having a proximal end 324 and a distal end 326, a cooling manifold328 mounted to the distal end 326 of the shaft 322, and an array 330 oftissue penetrating cooling needles 332 extending from the manifold 328.Like the cannula 312, the shaft 322 is composed of a suitable material,such as plastic, metal or the like. Like the shaft 322 of the ablationprobe assembly 106, it can be appreciated that longitudinal translationof the shaft 322 relative to the cannula 312 lathe dismal direction 138deploys the cooling needle array 330 from the distal end 318 of thecannula 312 (FIG. 14), and longitudinal translation of the shaft 322relative to the cannula 312 in the proximal direction 138 retracts thecooling needle array 330 into the distal end 318 of the cannula 312(FIG. 13).

The cooling needles 332 are of similar construction and composition asthe previously described needle electrodes 134. That is, each coolingneedle 332 is preferably composed of a single wire that is formed fromresilient conductive metals having a suitable shape memory, such asstainless steel, nickel-titanium alloys, nickel-chromium alloys, springsteel alloys, and the like. The wires may have circular or non-circularcross-sections. The distal ends of the cooling needles 332 may be honedor sharpened to facilitate their ability to penetrate tissue. The distalends of these cooling needles 332 may be hardened using conventionalheat treatment or other metallurgical processes. The diameter and lengthof the needles 332 are preferably within the range of 0.5 mm to 4.0 mm,and 5 cm to 25 cm, respectively.

When deployed from the cannula 312 (FIG. 14), the needle array 330 isplaced in a fan-shaped configuration. As with the previously describedneedle array 226, the needles 332 are arranged in a series to maximizethe cooling efficiency of cooling probe 310. In the illustratedembodiment, the needle array 330 is arranged in a rectilinear pattern,but can also be arranged in a curvilinear pattern or can be staggered.

The cooling probe 310 further comprises a handle assembly 334, whichincludes a connector sleeve 336 mounted to the proximal end 316 of thecannula 312 and a connector member 338 slidably engaged with the sleeve310 and mounted to the proximal end 324 of the shaft 322. The connectormember 338 of the handle assembly 334 comprises an inlet fluid port 340and an outlet fluid port 342. The handle assembly 334 can be composed ofany suitable rigid material, such as, e.g., metal, plastic, or the like.

Referring now to FIG. 15, the cooling probe 310 further comprises acoolant flow conduit (shown in phantom) that serves to cool the needles332, and thus the tissue in contact with the needle ray 330, bythermally drawing heat away. In particular, the coolant flow conduitcomprises a main cooling lumen 344 that is in fluid communication withthe inlet fluid port 340 of the handle assembly 334 and extends throughthe shaft 322, a network of cooling lumens 348 in fluid communicationwith the main cooling lumen 344 and extending through the coolingmanifold 328, and a plurality of cooling lumens 352 that are in fluidcommunication with the network of cooling lumens 348 and extend throughthe needles 332. The coolant flow conduit also comprises a main returnlumen 346 that is in fluid communication with the outlet fluid port 342of the handle assembly 334 and extends through the shaft 322, a networkof return lumens 348 in fluid communication with the main return lumen346 and extending through the cooling manifold 328, and a plurality ofreturn lumens 354 that are in fluid communication with the network ofreturn lumens 348 and extend through the needles 332. The distal ends ofthe cooling lumens 352 are in fluid communication with the respectivedistal ends of the return lumens 354 to complete the cooling circuit.

Operation of the cooling probe 310 is similar to the operation of thecooling probe 210, with the exception that the array of needles 332 canbe deployed during a percutaneous or laparoscopic procedure.Specifically, the electrode array 132 of the ablation probe assembly 106is deployed within the target tissue TR, as illustrated in FIG. 7. Theneedle array 330 of the cooling probe 312 is deployed from the distalend 318 of the cannula 312 into the tissue, so that the needles 332 liealong a boundary B separating the treatment region TR from thenon-treatment region NTR, as illustrated in FIG. 16A. The pump assembly114 is then operated to convey the cooling medium through the needles332, thereby providing a thermal barrier between the treatment region TRand the non treatment region NTR. Specifically, the power head 180conveys the cooled medium from the syringe 182 under positive pressure,through the tubing 198, and into the inlet fluid port 340 on the handle334. The cooled medium then travels though the main cooling lumen 344,through the network of cooling lumens 348 within the manifold 328, andinto the cooling lumens 352 within the needles 332. Thermal energy istransferred from the treatment region TR, to the needles 332, and thento the cooled medium, thereby preventing the thermal energy fromreaching the non-treatment region NTR and maintaining it at a cooltemperature. The heated medium is then conveyed from the return lumens354, through the network of return lumens 350 within the manifold 328,and into the main return lumen 346. From the main turn lumen 346, theheated medium travels through the outlet fluid port 342 on the handle334, through the tubing 199, and into the discharge reservoir 186.

The RF generator 108 is then operated to ablate the treatment region TR.Specifically, a lesion-L is formed within the treatment region TR, asillustrated in FIG. 16B. Because the actively cooled needle array 330forms a thermal barrier between the treatment region TR and thenon-treatment region NTR, the lesion L does not extend to thenon-treatment NTR, but instead exhibits a scalloped contour that extendsalong the barrier B.

Referring to FIG. 17, a single cooling needle 410 that can be used inthe cooling subsystem 104 is illustrated. The needle 410 comprises ashaft 412, a proximal end 414, and a distal end 416, and is composed ofa rigid thermally conductive material, such as, e.g., stainless steel.The needle 410 can have any cross-section as long as it is capable ofpenetrating tissue, but in the preferred embodiment, its cross-sectionis circular, oval or flat. The diameter and length of the needle 410 ispreferably within the range of 0.5 mm to 4.0 mm, and 5 cm to 25 cm,respectively. The needle 410 comprises an inlet fluid pot 418 and anoutlet fluid port 420 formed at its proximal end 414 for connection tothe pump assembly 114. The needle 410 further comprises a coolant flowconduit (shown in phantom) that serves to cool the shaft 412, and thusthe tissue in contact with the shaft 412, by thermally drawing heataway. In particular, the coolant flow conduit comprises a cooling lumen422 that is in fluid communication with the inlet fluid port 418 andextends through the shaft 412, and a return lumen 424 that is in fluidcommunication with the outlet fluid port 420 and extends through theshaft 412. The distal end of the cooling lumen 422 is in fluidcommunication with the distal end of the return lumen 424 to completethe cooling circuit.

Operation of the cooling needle 410 is similar to the operation of thecooling probe 310, with the exception that the cooling needle 410 ispercutaneously introduced through the skin of the patient or through asurgical opening into the tissue. Specifically, the electrode array 132of the ablation probe assembly 106 is deployed within the target tissueTR. The cooling needle 410 is inserted, percutaneously or through asurgical opening, into the tissue T on the boundary B separating thetreatment region TR from the non-treatment region NTR, as illustrated inFIG. 18A. The pump assembly 114 is then operated to convey the coolingmedium through the needle 410, thereby providing a thermal barrierbetween the treatment region TR and the non-treatment region NTR.Specifically, the power head 180 conveys the cooled medium from thesyringe 182 under positive pressure, through tubing 198, and into theinlet fluid port 418. The cooled medium then travels through the coolinglumen 422 of the needle 412. Thermal energy is transferred from thetreatment region TR, to the shaft 412 of the needle 410, and then to thecooled medium, thereby preventing the thermal energy from reaching thenon-treatment region NTR and maintaining it at a cool temperature. Theheated medium is then conveyed from the return lumen 424, through theoutlet fluid port 420, through the tubing 199, and into the dischargereservoir 186.

The RF generator 108 is then operated to ablate the treatment region TR.Specifically, a lesion L is formed within the treatment region TR, asillustrated in FIG. 18B. Because the actively cooled needle 410 forms athermal barrier between the treatment region TR and the non-treatmentregion NTR, the lesion L does not extend to the non-treatment NTR.

In alternative methods, multiple needles 410 can be inserted along thelength of the boundary B to provide a broader thermal barrier, in whichcase a scalloped lesion L will be formed similar to those illustrated inFIGS. 12B and 16B. The tubings 198 end 199 of the pump assembly 114 canbe branched in order to feed the medium to, and remove the heated mediumfrom, the multiple needles 410.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed is:
 1. A system comprising: a cooling shield comprising:an elongated shaft comprising an outer tubular element, an inner tubularelement disposed at least partially inside the outer tubular element,and a central tubular element; a balloon coupled at one end to the outertubular element and at an opposing end to the central tubular element,the balloon defining an interior region; a first fluid path interposedbetween the outer tubular element and the inner tubular element, thefirst fluid path in communication with the interior region of theballoon; a second fluid path interposed between the inner tubularelement and the central tubular lumen, the second fluid path incommunication with the interior region of the balloon; and an ablationprobe comprising: an elongate member having a proximal end and a distalend; an array of needles configured to extend from the distal end of theelongate member.
 2. The system of claim 1, wherein the array of needlesis arranged in a rectilinear pattern.
 3. The system of claim 1, whereinthe array of needles is arranged in a curvilinear pattern.
 4. The systemof claim 1, wherein the array of needles is staggered.
 5. The system ofclaim 1, wherein the array of needles is fan-shaped.
 6. The system ofclaim 1, wherein the array of needles is rake-shaped.
 7. The system ofclaim 1, further comprising a cooling pump assembly configured forpumping cooling medium through the cooling shield, and for pumpingheated cooling medium from the cooling shield.
 8. The system of claim 1,wherein the elongate member is flexible.
 9. The system of claim 1,wherein the elongate member is rigid.
 10. The system of claim 1, furthercomprising a cannula, wherein the elongate member is slidably disposedwithin the cannula, such that the array of needles can be selectivelydeployed from the cannula and retracted within the cannula.
 11. Thesystem of claim 10, wherein the cannula is configured to be introducedpercutaneously into a body of a patient.
 12. The system of claim 10,wherein the cannula is configured to be introduced laparoscopically intoa body of a patient.
 13. The system of claim 1, wherein the first fluidpath conveys a cooling medium and the second fluid path conveys a heatedcooling medium.
 14. The system of claim 1, wherein the second fluid pathconveys a cooling medium and the first fluid path conveys a heatedcooling medium.